The process of canonization in the earliest centuries of the church was performed by the local bishop (or the pope, if it was in the city of Rome) and by the popular acclamation of the local church. After an investigation was done, testimony was given by those who knew the candidate for sainthood, the faithful would give popular acclaim to the request, and the bishop would then enroll the name of the holy man or woman in the official liturgies and prayers of the church, alongside the other recognized  saints. Once canonized, or added to the official list of saints (the word “kanon” in Greek is “list”), the faithful could publically seek their intercession and venerate their relics. 

The legalization of Christianity led to administrative correspondence between the local bishops and the pope, resulting in the local church performing an investigation and scrutiny of the candidate, and then submitting their candidates for sainthood to the pope. It was a clear sign that a saint was not just for the veneration of the local church, but also for the universal church. After consultation with his theological advisors, the pope then held a solemn ceremony where he publically enrolled the name of the new saint along the other saints of the universal church. This ceremony was concluded with the acclamation of the faithful. The first saint canonized in a public papal canonization ceremony was Saint Ulrich, bishop of Augsburg (d. 973), who was canonized by Pope John XV at the Latern Council in 993 AD.

The rite of canonization used today still maintains these historical and theological traditions passed down from the early Church. Today, a canonization takes place by the pope in a public Mass, either in Rome or in a region associated with the new saint. The rite begins by the chanting of the Litany of Saints, the list of saints that this new saints is about to be added to. Each name in the litany is followed by the people responding “Ora pro Nobis” (pray for us), showing the church on earth seeking the intercession of the saints in heaven. The Prefect of the Congregation of the Causes of Saints (the Vatican Office that oversees the investigation) then comes forward, and in the name of the universal church, makes three petitions to the pope. The petitions testify that the candidate has been found worthy by both investigation and a miracle, and now the church ask the pope to invoke his supreme authority to enter this candidate’s name in the canon (official list) of saints. The pope responds by pronouncing the canonization formula, thus granting universal veneration, and adding that name to the list of saints. 

When the rite of canonization is complete, the relics of the saint are brought forward to the pope, who incenses them, and presents them to the faithful for public veneration. This liturgical act states that the saint may receive public veneration (ie., their relics placed in an altar, churches may be dedicated to them, feast days placed on liturgical calendars). In the name of all the faithful, the prefect then thanks the pope for this action, and requests an official document. The pope responds ”Decernimus” (We so degree). Those gathered at the Mass then show their consent and affirmation by applause. The canonization Mass then continues with the singing of the “Gloria”, the Church’s hymn of thanksgiving to God.